Low-cost and large-area uniform amorphous Ga_(2)O_(3)(α-Ga_(2)O_(3))solar-blind ultraviolet(UV)detectors have garnered significant attention in recent years.Oxygen vacancy(VO)defects are generally considered as the p...Low-cost and large-area uniform amorphous Ga_(2)O_(3)(α-Ga_(2)O_(3))solar-blind ultraviolet(UV)detectors have garnered significant attention in recent years.Oxygen vacancy(VO)defects are generally considered as the predominant defects affecting the detector performance.Reducing VOconcentration generally results in both low dark current and low photo current,significantly limiting further improvement of the photo-to-dark current ratio(PDCR)parameter.Herein,a delicately optimized atomic layer deposition(ALD)method is revealed having the capability to break through the trade-off in a-Ga_(2)O_(3),achieving both low dark current and high photocurrent simultaneously.For a clear demonstration,a-Ga_(2)O_(3)contrast sample is prepared by magnetron sputtering and compared as well.Combined tests are performed including xray photoelectron spectroscopy,photoluminescence,electron paramagnetic resonance and Fourier-transform infrared spectroscopy.It is found that ALDα-Ga_(2)O_(3)has a lower VOconcentration,but also a lower dangling bonds concentration which are strong non-irradiation recombination centers.Therefore,decrease of dangling bonds is suggested to compensate for the low optical gain induced by low VOconcentration and promote the PDCR to~2.06×10^(6).Our findings firstly prove that the dangling bonds also play an important role in determining the a-Ga_(2)O_(3)detection performance,offering new insights for further promotion ofα-Ga_(2)O_(3)UV detector performance via dual optimization of dangling bonds and VO.展开更多
We have investigated the effect of surface dangling bonds and molecular passivation on the doping of GaAs nanowires by first-principles calculations. Results show that the positively charged surface dangling bond on G...We have investigated the effect of surface dangling bonds and molecular passivation on the doping of GaAs nanowires by first-principles calculations. Results show that the positively charged surface dangling bond on Ga atom is the most stable defect for both ultrathin and large size GaAs nanowires. It can form the trap centers of holes and then prefer to capture the holes from p-type doping. Thus it could obviously reduce the efficiency of the p-type doping. We also found that the NO2 molecule is electronegative enough to capture the unpaired electrons of surface dangling bonds, which is an ideal passivation material for the Zn-doped GaAs nanowires.展开更多
As the owner of Nobel Prize for Literature, Saul Bellow＇s （1915-2005） fiction has always been a great concern in literary world. It has been studied from various perspectives since its publication. While comparativ...As the owner of Nobel Prize for Literature, Saul Bellow＇s （1915-2005） fiction has always been a great concern in literary world. It has been studied from various perspectives since its publication. While comparatively speaking, few studies were made from the historical lens. Actually, in his fiction, history is presented by fiction which contributes to the making of history. The purpose of the present paper is through close reading of his novels to find out the different historic periods of American Jews from ＂the strangers＂ to ＂the natives＂, the ＂More than Human＂ and ＂Less than Human＂ to the ＂Exact Human＂ presented in his fiction and thus help readers to have a better understanding about the Jewish life and identity.展开更多
Saul Bellow’s novel Seize the Day combines the psychological narrative of Jewish immigrants in the“Happy Age”of the United States and the daily life narrative of modern New York urbanites,revealing the living state...Saul Bellow’s novel Seize the Day combines the psychological narrative of Jewish immigrants in the“Happy Age”of the United States and the daily life narrative of modern New York urbanites,revealing the living state of modern urbanites-powerless to the outside world,nowhere to live in the material and spiritual world.They have an unresolved personal pursuit and a“dangling”destiny,which alludes to the problems plaguing modern urban people and the decay of American society.By comparing the characteristics and fate of the protagonist Wilhelm with the character Job in the Bible,this article helps to deepen the understanding of the plights of the protagonist as“Modern Job”,and realize the influence of the American urban society on Jewishness and personal survival in that period.展开更多
Photocatalytic water oxidation reaction by transition metal complexes remains a challenge because of their poor stability under irradiation,especially for earth-abundant metal catalysts.In this regard,ironbased water ...Photocatalytic water oxidation reaction by transition metal complexes remains a challenge because of their poor stability under irradiation,especially for earth-abundant metal catalysts.In this regard,ironbased water oxidation catalysts are prone to hydrolysis and/or dissociate the ligands to form nanoparticles under a real catalytic condition.Herein,we describe a unique hexa-coordinated catalyst 1[Fe^(II)(Py_(3)tacn)Cl_(2)]and its reference 2[Fe^(II)(PhPy_(2)tacn)Cl_(2)]with a dangling pyridyl ligand and a phenyl group,respectively.We anticipated that the dynamically open and close coordination behaviors of the pyridyl ligand enabled balance of the reactivity and stability of catalyst 1.To our delight,the“open form”of catalyst 1 provided a free coordination site,and the“close form”guaranteed its molecular integrity,resulting in a water oxidation reaction with high efficiency and robustness.The turnover number and turnover frequency values of 2332 and 60 s^(−1)are the highest known to date among iron-based homogeneous water oxidation systems under visible light irradiation.展开更多
The lead-free inorganic perovskite CsSnI_(3) is considered as one of the best candidates for emerging photovoltaics.Nevertheless,CsSnI_(3)-based perovskite solar cells experience a significant drop in performance due ...The lead-free inorganic perovskite CsSnI_(3) is considered as one of the best candidates for emerging photovoltaics.Nevertheless,CsSnI_(3)-based perovskite solar cells experience a significant drop in performance due to the nonradiative recombination facilitated by trapping.Here,we show an electron donor passivation method to regulate deep-level defects for CsSnI_(3) perovskite with electron donor pyrrole.Experimental observations combined with theoretical simulations verify that the saturation of Tin dangling bonds with pyrrole on the CsSnI_(3) surface via a Lewis acid-base addition reaction can significantly reduce the density of deep-level defects.Consequently,the printable mesoporous perovskite solar cells with an FTO/compact-TiO_(2)/mesoporous-TiO_(2)/Al_(2)O_(3)/NiO/carbon framework device structure penetrated with CsSnI_(3) achieve a power conversion efficiency of up to 10.11%.To our knowledge,this represents the highest efficiency reported to date for lead-free pero vs kite-based printable mesoporous solar cells.Furthermore,the unencapsulated devices demonstrated remarkable long-term stability,retaining 92%of their initial efficiency even after 2400 h of aging in a nitrogen atmosphere.展开更多
Though GaN nanoribbons （GaNNRs） with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except f...Though GaN nanoribbons （GaNNRs） with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except for the armchair edge GaNNRs （AGaNNRs） with bare N and Ga edges, which are still nonmagnetic semiconductors due to the strong coupling of the dangling bonds of dimeric N and Ga atoms at the same edge. The larger difference in the charge density （pUp_pdown） for edge bare N atoms and decaying for N sub-lattices away from the edge, as well as the smaller difference in the charge density for edge bare Ga atoms and without decaying for Ga sub-lattices away from the edge is consistent with the magnetic moment of a GaNNR with bare N edge being larger than that of a GaNNR with bare Ga edge. The magnetic moment of a zigzag edge GaNNR （ZGaNNR） with bare N （Ga） edge has nearly half the value of the magnetic moment of a AGaNNR with bare N （Ga） edge. Such a relationship also exists in the number of extra dangling bond states appearing around the Fermi level in the band structures. For ZGaNNRs, the magnetic moment of bare N and Ga edges is larger than either bare N edge or bare Ga edge, but smaller than their sum, implying that there exists an interaction between the dangling bonds at both edges of bare N and Ga edges.展开更多
6H-SiC is an important semiconductor material. The 6H-SiC wafer is always exposed to a high-humidity environment and the effect from the absorbed water molecule and some relative adsorbates is not negligible. Here, th...6H-SiC is an important semiconductor material. The 6H-SiC wafer is always exposed to a high-humidity environment and the effect from the absorbed water molecule and some relative adsorbates is not negligible. Here, the oxygen and water molecules absorbed on the 6H-SiC(0001) surface and the dissociation process were studied with density functional theory. On the 6H-SiC(0001) surface, absorbed O2 is spontaneously dissociated into O*, which is absorbed on a hollow site, and further transforms the 6H-SiC(0001) surface into SiO2. The absorbed H2O is spontaneously broken into OH*and H*, which are both absorbed on the top of the Si atom, and OH* is further reversibly transformed into O* and H*. The H* could saturate the dangling Si bond and change the absorption type of O*, which could stabilize the 6H-SiC(0001) surface and prevent it from transforming into SiO2.展开更多
The self-activated (SA) luminescence in ZnS nanoparticles was studied by comparing the UV-light irradiation induced spectral change, Raman spectra, and EPR spectra of the un-rinsed and rinsed samples. The results show...The self-activated (SA) luminescence in ZnS nanoparticles was studied by comparing the UV-light irradiation induced spectral change, Raman spectra, and EPR spectra of the un-rinsed and rinsed samples. The results show that the SA centers prefer to occupy the sites near the surface and that the donor of SA emission may be related to organic functional groups such as -OH, -CH 3, and -COO. The EPR signals are enhanced remarkably in the rinsed nanoparticles comparing with that in the un-rinsed ones. It is believed that organic functional groups physically combine with the surface dangling bonds of ZnS nanoparticles, leading the nonradiative transition channels to decrease, and thus the SA emission to increase.展开更多
Photoluminescence （PL） spectra of Si nanocrystals （NCs） prepared by 130 keV Si ions implantation onto SiO2 matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist...Photoluminescence （PL） spectra of Si nanocrystals （NCs） prepared by 130 keV Si ions implantation onto SiO2 matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist of two PL peaks, originated from smaller Si NCs due to quantum confinement effect （QCE） and the interface states located at the surface of larger Si NCs. The evolution of number of dangling bonds （DBs） on Si NCs was also investigated. For bydrogen-passivated samples, a monotonic increase in PL peak intensity with the dose of implanted Si ions up to 3× 10^17 ions/cm^2 is observed. The number of DBs on individual Si NC, the interaction between DBs at the surface of neighbouring Si NCs and their effects on the efficiency of PL are discussed.展开更多
This paper uses a molecular static approach with a many-body potential to investigate the surface energetic and bonding characteristics of tetrahexahedral platinum nanocrystals enclosed by high-index facets such as {2...This paper uses a molecular static approach with a many-body potential to investigate the surface energetic and bonding characteristics of tetrahexahedral platinum nanocrystals enclosed by high-index facets such as {210}, {310}, {410}, {520} and {730}. It mainly focuses on the effect of crystal size and surface Miller index on these characteristics. The results show that the surface energy and dangling bond density increase with decreasing diameter of tetrahexahedral nanocrystals and generally show an order of {210} 〉{730}〉 {520} 〉 {310} 〉 {410}. However, this order is not valid at crystal sizes below 7 nm or so. The results of corresponding surfaces are also presented for comparison.展开更多
The properties of temperature dependence of conductivity σ of electron beam evaporated a-Si_(1-x)Gd_x films which was deposited on some substrates of glass and Al-foil at a substrate temperature of approximately 300...The properties of temperature dependence of conductivity σ of electron beam evaporated a-Si_(1-x)Gd_x films which was deposited on some substrates of glass and Al-foil at a substrate temperature of approximately 300℃ in a background pressure about 2×10^(-4) Pa with a deposition speed about 0.2 nm/s was analyzed and studied.The forms of Gd^(3+) ions in the films,the dangling bond compensation achieved by Gd^(3+) ions and the impurity states compensation achieved by structural disorder aroused by doping Gd ele- ment into a-Si film could be the key factors in resolving the properties of conduction in a-Si_(1-x)Gd_x films.In the temperature region of 290 K<T<500 K,an analysis of conductivity allows to reveal two conductivity regions:(1)conducting conduction of the carriers excited to conductive band,(2)hopping conduction of the carriers in the impurity band near E_F level thermo-excited.展开更多
Photoluminescence （PL） intensity of passivated silicon nanocrystals （Si NCs） embedded in a SiO2 matrix is com- pared with that of unpassivated Si NCs. We investigate the relative enhancement of PL intensity （IR）...Photoluminescence （PL） intensity of passivated silicon nanocrystals （Si NCs） embedded in a SiO2 matrix is com- pared with that of unpassivated Si NCs. We investigate the relative enhancement of PL intensity （IR） as a function of annealing temperature and implanted Si ion dose. The IR increases simultaneously with the annealing temperature. This demonstrates an increase in the number of dangling bonds （DBs） with the degree of Si crystallization varying via the annealing temperature. The increase in IR with implanted Si ion dose is also observed. We believe that the near-field interaction between DBs and neighboring Si NCs is an additional factor that reduces the PL efficiency of unpassivated Si NCs.展开更多
Based on the empirical electron surface model （EESM）,the covalent electron density of dangling bonds （CEDDB） was calculated for various crystal planes of gold,and the surface energy was calculated further.Calculat...Based on the empirical electron surface model （EESM）,the covalent electron density of dangling bonds （CEDDB） was calculated for various crystal planes of gold,and the surface energy was calculated further.Calculation results show that CEDDB has a great influence on the surface energy of various index surfaces and the anisotropy of the surface.The calculated surface energy is in agreement with experimental and other theoretical values.The calculated surface energy of the close-packed （111） surface has the lowest surface energy,which agrees with the theoretical prediction.Also,it is found that the spatial distribution of covalent bonds has a great influence on the surface energy of various index surfaces.Therefore,CEDDB should be a suitable parameter to describe and quantify the dangling bonds and surface energy of various crystal surfaces.展开更多
Hydrogenated amorphous silicon(a-Si:H)has a long history in the development of photovoltaics,especially in the research field of a-Si:H thin-film solar cells and crystalline/amorphous silicon heterojunction solar cell...Hydrogenated amorphous silicon(a-Si:H)has a long history in the development of photovoltaics,especially in the research field of a-Si:H thin-film solar cells and crystalline/amorphous silicon heterojunction solar cells.More than 40 years ago,Staebler and Wronski reported conductance decrease of a-Si:H induced by light soaking.This phenomenon has been widely investigated for electronic applications.In contrast to that,we found light soaking can also improve dark conductance of a-Si:H when boron or phosphorus atoms are doped into the amorphous network.Here we survey these two photoelectronic effects,and discuss their implementations to silicon solar cells.展开更多
The emerging applications of composite gels as thermal interface ma-terials(TIMs)for chip heat dissipation in intelligent vehicle and wear-able devices require high thermal conductivity and remarkable damp-ing propert...The emerging applications of composite gels as thermal interface ma-terials(TIMs)for chip heat dissipation in intelligent vehicle and wear-able devices require high thermal conductivity and remarkable damp-ing properties.However,thermal conductivity and damping proper-ties are usually correlated and coupled each other.Here,inspired by Maxwell theory and adhesion mechanism of gecko’s setae,we present a strategy to fabricate polydimethylsiloxane-based composite gels in-tegrating high thermal conductivity and remarkable damping prop-erties over a broad frequency and temperature range.The multiple relaxation modes of dangling chains and the dynamic interaction be-tween the dangling chains and aluminum fillers can efficiently dis-sipate the vibration energy,endowing the composite gels with ultra-high damping property(tanδ>0.3)over a broad frequency(0.01-100 Hz)and temperature range(-50-150°C),which exceeds typi-cal state-of-the-art damping materials.The dangling chains also com-fort to the interfaces between polymer matrix and aluminum via van der Waals interaction,resulting in high thermal conductivity(4.72±0.04 W m-1 K-1).Using the polydimethylsiloxane-based composite gel as TIMs,we demonstrate effective heat dissipation in chip oper-ating under vigorous vibrations.We believe that our strategy could be applied to a wide range of composite gels and lead to the devel-opment of high-performance composite gels as TIMs for chip heat dissipation.展开更多
Ⅰ. INTRODUCTION Hydrogenated amorphous silicon-carbon (a-Si1-xCx:H) film is an important amorphous photoelectric semiconductor material having a wide and variable band gap. It reduces the interface reflection and sur...Ⅰ. INTRODUCTION Hydrogenated amorphous silicon-carbon (a-Si1-xCx:H) film is an important amorphous photoelectric semiconductor material having a wide and variable band gap. It reduces the interface reflection and surface absorption of incident light when it展开更多
Since the beginning of the 1980’s, we have been studying the physical properties of laserprepared nanometer silicon nitride by a series of experiments, and observed many new physical phenomena such as the distortion ...Since the beginning of the 1980’s, we have been studying the physical properties of laserprepared nanometer silicon nitride by a series of experiments, and observed many new physical phenomena such as the distortion of the infrared absorption peaks, the full infrared absorption and the distortion of Raman shift. In this note, we study the fluorescence spectra of laser-prepared nanometer amorphous silicon nitride powder and bulk for the first time,展开更多
By means of the polymer statistical theory, the A_f-A_g type nonlinear free radical polymerization is investigated to give the number of effective elastic chains, the number of effective elastic mers and the average l...By means of the polymer statistical theory, the A_f-A_g type nonlinear free radical polymerization is investigated to give the number of effective elastic chains, the number of effective elastic mers and the average length for the elastic chains. The corresponding quantities for the dangling chains, the number of effective cross-linkage and the modulus are also obtained. Furthermore, the number- and weight-fractions of elastic chains are deduced.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62404146,12174275,62174113)the Basic and Applied Basic Research Foundation of Guangdong Province,China(Grant Nos.2023A1515110730 and 2023A1515140094)the INTPART Program at the Research Council of Norway(Project number 322382)。
文摘Low-cost and large-area uniform amorphous Ga_(2)O_(3)(α-Ga_(2)O_(3))solar-blind ultraviolet(UV)detectors have garnered significant attention in recent years.Oxygen vacancy(VO)defects are generally considered as the predominant defects affecting the detector performance.Reducing VOconcentration generally results in both low dark current and low photo current,significantly limiting further improvement of the photo-to-dark current ratio(PDCR)parameter.Herein,a delicately optimized atomic layer deposition(ALD)method is revealed having the capability to break through the trade-off in a-Ga_(2)O_(3),achieving both low dark current and high photocurrent simultaneously.For a clear demonstration,a-Ga_(2)O_(3)contrast sample is prepared by magnetron sputtering and compared as well.Combined tests are performed including xray photoelectron spectroscopy,photoluminescence,electron paramagnetic resonance and Fourier-transform infrared spectroscopy.It is found that ALDα-Ga_(2)O_(3)has a lower VOconcentration,but also a lower dangling bonds concentration which are strong non-irradiation recombination centers.Therefore,decrease of dangling bonds is suggested to compensate for the low optical gain induced by low VOconcentration and promote the PDCR to~2.06×10^(6).Our findings firstly prove that the dangling bonds also play an important role in determining the a-Ga_(2)O_(3)detection performance,offering new insights for further promotion ofα-Ga_(2)O_(3)UV detector performance via dual optimization of dangling bonds and VO.
基金This work was supported by the National Basic Research Program of China （No.2010CB327600）, the National Natural Science Foundation of China （No.61020106007 and No.61376019）, the Natural Science Foundation of Beijing （No.4142038）, the Specialized Research Fund for the Doctoral Program of Higher Education （No.20120005110011）, and the 111 Program of China （No.B07005）. Jian-gong Cui would like to thank Dr. Xin Yan and Dr. Jun-shuai Li from Beijing University of Posts and Telecommunications for useful discussions.
文摘We have investigated the effect of surface dangling bonds and molecular passivation on the doping of GaAs nanowires by first-principles calculations. Results show that the positively charged surface dangling bond on Ga atom is the most stable defect for both ultrathin and large size GaAs nanowires. It can form the trap centers of holes and then prefer to capture the holes from p-type doping. Thus it could obviously reduce the efficiency of the p-type doping. We also found that the NO2 molecule is electronegative enough to capture the unpaired electrons of surface dangling bonds, which is an ideal passivation material for the Zn-doped GaAs nanowires.
文摘As the owner of Nobel Prize for Literature, Saul Bellow＇s （1915-2005） fiction has always been a great concern in literary world. It has been studied from various perspectives since its publication. While comparatively speaking, few studies were made from the historical lens. Actually, in his fiction, history is presented by fiction which contributes to the making of history. The purpose of the present paper is through close reading of his novels to find out the different historic periods of American Jews from ＂the strangers＂ to ＂the natives＂, the ＂More than Human＂ and ＂Less than Human＂ to the ＂Exact Human＂ presented in his fiction and thus help readers to have a better understanding about the Jewish life and identity.
文摘Saul Bellow’s novel Seize the Day combines the psychological narrative of Jewish immigrants in the“Happy Age”of the United States and the daily life narrative of modern New York urbanites,revealing the living state of modern urbanites-powerless to the outside world,nowhere to live in the material and spiritual world.They have an unresolved personal pursuit and a“dangling”destiny,which alludes to the problems plaguing modern urban people and the decay of American society.By comparing the characteristics and fate of the protagonist Wilhelm with the character Job in the Bible,this article helps to deepen the understanding of the plights of the protagonist as“Modern Job”,and realize the influence of the American urban society on Jewishness and personal survival in that period.
基金support from the National Key Research and Development Program of China(grant nos.2022YFA1502900,2022YFA0911900,2021YFA1500800,and 2022YFB3803600)the National Natural Science Foundation of China(grant nos.20231001,22201288,21933007,22193013,and 22088102)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Science(grant no.XDB17000000)the New Cornerstone Science Foundation.
文摘Photocatalytic water oxidation reaction by transition metal complexes remains a challenge because of their poor stability under irradiation,especially for earth-abundant metal catalysts.In this regard,ironbased water oxidation catalysts are prone to hydrolysis and/or dissociate the ligands to form nanoparticles under a real catalytic condition.Herein,we describe a unique hexa-coordinated catalyst 1[Fe^(II)(Py_(3)tacn)Cl_(2)]and its reference 2[Fe^(II)(PhPy_(2)tacn)Cl_(2)]with a dangling pyridyl ligand and a phenyl group,respectively.We anticipated that the dynamically open and close coordination behaviors of the pyridyl ligand enabled balance of the reactivity and stability of catalyst 1.To our delight,the“open form”of catalyst 1 provided a free coordination site,and the“close form”guaranteed its molecular integrity,resulting in a water oxidation reaction with high efficiency and robustness.The turnover number and turnover frequency values of 2332 and 60 s^(−1)are the highest known to date among iron-based homogeneous water oxidation systems under visible light irradiation.
基金supported by the National Key Research and Development Program of China(2022YFB4200305)the National Natural Science Foundation of China(22379049)Hubei Provincial Key Research and Development Program(2023BAB113)。
文摘The lead-free inorganic perovskite CsSnI_(3) is considered as one of the best candidates for emerging photovoltaics.Nevertheless,CsSnI_(3)-based perovskite solar cells experience a significant drop in performance due to the nonradiative recombination facilitated by trapping.Here,we show an electron donor passivation method to regulate deep-level defects for CsSnI_(3) perovskite with electron donor pyrrole.Experimental observations combined with theoretical simulations verify that the saturation of Tin dangling bonds with pyrrole on the CsSnI_(3) surface via a Lewis acid-base addition reaction can significantly reduce the density of deep-level defects.Consequently,the printable mesoporous perovskite solar cells with an FTO/compact-TiO_(2)/mesoporous-TiO_(2)/Al_(2)O_(3)/NiO/carbon framework device structure penetrated with CsSnI_(3) achieve a power conversion efficiency of up to 10.11%.To our knowledge,this represents the highest efficiency reported to date for lead-free pero vs kite-based printable mesoporous solar cells.Furthermore,the unencapsulated devices demonstrated remarkable long-term stability,retaining 92%of their initial efficiency even after 2400 h of aging in a nitrogen atmosphere.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51071098 and 11104175)the State Key Development for Basic Research of China (Grant No. 2010CB631002)
文摘Though GaN nanoribbons （GaNNRs） with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except for the armchair edge GaNNRs （AGaNNRs） with bare N and Ga edges, which are still nonmagnetic semiconductors due to the strong coupling of the dangling bonds of dimeric N and Ga atoms at the same edge. The larger difference in the charge density （pUp_pdown） for edge bare N atoms and decaying for N sub-lattices away from the edge, as well as the smaller difference in the charge density for edge bare Ga atoms and without decaying for Ga sub-lattices away from the edge is consistent with the magnetic moment of a GaNNR with bare N edge being larger than that of a GaNNR with bare Ga edge. The magnetic moment of a zigzag edge GaNNR （ZGaNNR） with bare N （Ga） edge has nearly half the value of the magnetic moment of a AGaNNR with bare N （Ga） edge. Such a relationship also exists in the number of extra dangling bond states appearing around the Fermi level in the band structures. For ZGaNNRs, the magnetic moment of bare N and Ga edges is larger than either bare N edge or bare Ga edge, but smaller than their sum, implying that there exists an interaction between the dangling bonds at both edges of bare N and Ga edges.
基金supported by the Fundamental Research Project of Qinghai Province (2017-ZJ-795)
文摘6H-SiC is an important semiconductor material. The 6H-SiC wafer is always exposed to a high-humidity environment and the effect from the absorbed water molecule and some relative adsorbates is not negligible. Here, the oxygen and water molecules absorbed on the 6H-SiC(0001) surface and the dissociation process were studied with density functional theory. On the 6H-SiC(0001) surface, absorbed O2 is spontaneously dissociated into O*, which is absorbed on a hollow site, and further transforms the 6H-SiC(0001) surface into SiO2. The absorbed H2O is spontaneously broken into OH*and H*, which are both absorbed on the top of the Si atom, and OH* is further reversibly transformed into O* and H*. The H* could saturate the dangling Si bond and change the absorption type of O*, which could stabilize the 6H-SiC(0001) surface and prevent it from transforming into SiO2.
文摘The self-activated (SA) luminescence in ZnS nanoparticles was studied by comparing the UV-light irradiation induced spectral change, Raman spectra, and EPR spectra of the un-rinsed and rinsed samples. The results show that the SA centers prefer to occupy the sites near the surface and that the donor of SA emission may be related to organic functional groups such as -OH, -CH 3, and -COO. The EPR signals are enhanced remarkably in the rinsed nanoparticles comparing with that in the un-rinsed ones. It is believed that organic functional groups physically combine with the surface dangling bonds of ZnS nanoparticles, leading the nonradiative transition channels to decrease, and thus the SA emission to increase.
文摘Photoluminescence （PL） spectra of Si nanocrystals （NCs） prepared by 130 keV Si ions implantation onto SiO2 matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist of two PL peaks, originated from smaller Si NCs due to quantum confinement effect （QCE） and the interface states located at the surface of larger Si NCs. The evolution of number of dangling bonds （DBs） on Si NCs was also investigated. For bydrogen-passivated samples, a monotonic increase in PL peak intensity with the dose of implanted Si ions up to 3× 10^17 ions/cm^2 is observed. The number of DBs on individual Si NC, the interaction between DBs at the surface of neighbouring Si NCs and their effects on the efficiency of PL are discussed.
基金Project supported by the International Science & Technology Cooperation Project of China (Grant No 2007DFA40890)the National Natural Science Foundation of China (Grant Nos 10702056 and 10774124)the Program for New Century Excellent Talents in Fujian Province University, China
文摘This paper uses a molecular static approach with a many-body potential to investigate the surface energetic and bonding characteristics of tetrahexahedral platinum nanocrystals enclosed by high-index facets such as {210}, {310}, {410}, {520} and {730}. It mainly focuses on the effect of crystal size and surface Miller index on these characteristics. The results show that the surface energy and dangling bond density increase with decreasing diameter of tetrahexahedral nanocrystals and generally show an order of {210} 〉{730}〉 {520} 〉 {310} 〉 {410}. However, this order is not valid at crystal sizes below 7 nm or so. The results of corresponding surfaces are also presented for comparison.
文摘The properties of temperature dependence of conductivity σ of electron beam evaporated a-Si_(1-x)Gd_x films which was deposited on some substrates of glass and Al-foil at a substrate temperature of approximately 300℃ in a background pressure about 2×10^(-4) Pa with a deposition speed about 0.2 nm/s was analyzed and studied.The forms of Gd^(3+) ions in the films,the dangling bond compensation achieved by Gd^(3+) ions and the impurity states compensation achieved by structural disorder aroused by doping Gd ele- ment into a-Si film could be the key factors in resolving the properties of conduction in a-Si_(1-x)Gd_x films.In the temperature region of 290 K<T<500 K,an analysis of conductivity allows to reveal two conductivity regions:(1)conducting conduction of the carriers excited to conductive band,(2)hopping conduction of the carriers in the impurity band near E_F level thermo-excited.
基金Project supported by the State Key Laboratory of Nuclear Physics and Technology, China
文摘Photoluminescence （PL） intensity of passivated silicon nanocrystals （Si NCs） embedded in a SiO2 matrix is com- pared with that of unpassivated Si NCs. We investigate the relative enhancement of PL intensity （IR） as a function of annealing temperature and implanted Si ion dose. The IR increases simultaneously with the annealing temperature. This demonstrates an increase in the number of dangling bonds （DBs） with the degree of Si crystallization varying via the annealing temperature. The increase in IR with implanted Si ion dose is also observed. We believe that the near-field interaction between DBs and neighboring Si NCs is an additional factor that reduces the PL efficiency of unpassivated Si NCs.
基金supported by the Beijing Natural Science Foundation,China (No.2072014)the Ph.D. Program Foundation of the Ministry of Education of China (No.200800100006)
文摘Based on the empirical electron surface model （EESM）,the covalent electron density of dangling bonds （CEDDB） was calculated for various crystal planes of gold,and the surface energy was calculated further.Calculation results show that CEDDB has a great influence on the surface energy of various index surfaces and the anisotropy of the surface.The calculated surface energy is in agreement with experimental and other theoretical values.The calculated surface energy of the close-packed （111） surface has the lowest surface energy,which agrees with the theoretical prediction.Also,it is found that the spatial distribution of covalent bonds has a great influence on the surface energy of various index surfaces.Therefore,CEDDB should be a suitable parameter to describe and quantify the dangling bonds and surface energy of various crystal surfaces.
基金supports from National Natural Science Foundations of China(Nos.T2322028,62004208,62074153)Science and Technology Commission of Shanghai Municipality(No.22ZR1473200)+1 种基金Talent plan of Shanghai Branch,Chinese Academy of Sciences(No.CASSHB-QNPD-2023-001)Shanghai Rising-Star Program(No.23QA1411100).
文摘Hydrogenated amorphous silicon(a-Si:H)has a long history in the development of photovoltaics,especially in the research field of a-Si:H thin-film solar cells and crystalline/amorphous silicon heterojunction solar cells.More than 40 years ago,Staebler and Wronski reported conductance decrease of a-Si:H induced by light soaking.This phenomenon has been widely investigated for electronic applications.In contrast to that,we found light soaking can also improve dark conductance of a-Si:H when boron or phosphorus atoms are doped into the amorphous network.Here we survey these two photoelectronic effects,and discuss their implementations to silicon solar cells.
基金This work was supported by the National Key Research and Development Program of China(No.2020YFB040176)National Natural Science Foundation of China(No.52073300 and 62104161)+3 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2019354)Guangdong Province Key Field R&D Program Project(No.2020B010190004),Shenzhen Science and Technology Research Funding(No.JCYJ20200109114401708)Key Project of Science and Technol-ogy of Changsha(kq2102005)Guangdong Provincial Key Laboratory(2014B030301014).
文摘The emerging applications of composite gels as thermal interface ma-terials(TIMs)for chip heat dissipation in intelligent vehicle and wear-able devices require high thermal conductivity and remarkable damp-ing properties.However,thermal conductivity and damping proper-ties are usually correlated and coupled each other.Here,inspired by Maxwell theory and adhesion mechanism of gecko’s setae,we present a strategy to fabricate polydimethylsiloxane-based composite gels in-tegrating high thermal conductivity and remarkable damping prop-erties over a broad frequency and temperature range.The multiple relaxation modes of dangling chains and the dynamic interaction be-tween the dangling chains and aluminum fillers can efficiently dis-sipate the vibration energy,endowing the composite gels with ultra-high damping property(tanδ>0.3)over a broad frequency(0.01-100 Hz)and temperature range(-50-150°C),which exceeds typi-cal state-of-the-art damping materials.The dangling chains also com-fort to the interfaces between polymer matrix and aluminum via van der Waals interaction,resulting in high thermal conductivity(4.72±0.04 W m-1 K-1).Using the polydimethylsiloxane-based composite gel as TIMs,we demonstrate effective heat dissipation in chip oper-ating under vigorous vibrations.We believe that our strategy could be applied to a wide range of composite gels and lead to the devel-opment of high-performance composite gels as TIMs for chip heat dissipation.
文摘Ⅰ. INTRODUCTION Hydrogenated amorphous silicon-carbon (a-Si1-xCx:H) film is an important amorphous photoelectric semiconductor material having a wide and variable band gap. It reduces the interface reflection and surface absorption of incident light when it
文摘Since the beginning of the 1980’s, we have been studying the physical properties of laserprepared nanometer silicon nitride by a series of experiments, and observed many new physical phenomena such as the distortion of the infrared absorption peaks, the full infrared absorption and the distortion of Raman shift. In this note, we study the fluorescence spectra of laser-prepared nanometer amorphous silicon nitride powder and bulk for the first time,
基金Project supported by the National Natural Science Foundation of China (Grant No. 29673018)the Ph. D. funds of the State Education Commission of China
文摘By means of the polymer statistical theory, the A_f-A_g type nonlinear free radical polymerization is investigated to give the number of effective elastic chains, the number of effective elastic mers and the average length for the elastic chains. The corresponding quantities for the dangling chains, the number of effective cross-linkage and the modulus are also obtained. Furthermore, the number- and weight-fractions of elastic chains are deduced.
